Speed regulating systems that compare actual vehicle speed to pre-set values are effective in monitoring and controlling vehicle performance over a given course. Such systems may be used in commercial vehicles, such as trucks, and noncommercial vehicles to prevent over- and under-speeding in order to improve fuel economy. Speed regulating systems generally allow a vehicle operator to select a vehicle set-speed and the system monitors actual vehicle speed in relation to the set-speed, controlling engine performance in order to maintain actual vehicle speed at the set-speed. Speed regulation is effectuated by regulating fuel flow to the vehicle's engine by detecting deviation from the set-speed and adjusting the fuel flow to reduce or eliminate the deviation. If the speed regulating system detects an under-speed condition, such as might occur while the vehicle traverses up a hill, the system commands an increase in fuel flow to increase vehicle speed. Alternatively, if the system detects an over-speed condition, such as might occur while the vehicle traverse down a hill, the system commands a decrease in fuel flow to decrease vehicle speed.